What Does Refresh Do?

Refresh just updates the information on the screen.

Say you have a folder open and then open Word and make a document. Then you save that document to the open folder (using File/Save or File/Save As). The folder won't show the document. The document will appear on the folder only after you refresh.

For some reason, Microsoft didn't put an auto-refresh feature in Windows. I don't know about Macs but Windows doesn't have this feature.

Can you be more specific than "on our computer screen"?

This could potentially be a "deep" question about how GUI programs interact with the OS, but I don't want to go there if the other poster already answered your question.

please tell us about how GUI interacts with OS we really want to know about it or if you can refer some book or website to know about it.

Its been a few years since I've done any Windows programming but the basic idea for MS Windows is that it will will send a Refresh or Paint request/command to all of the application(s) that it wants to refresh and each application is to respond to the request by rePainting its client window. If the Refresh is for the entire desktop, then each application that is not minimized will get a RePaint/Refresh request ciommand. If the Refresh is just for a specific area of a client's window then the request will be just sent to the appication that owns that window. Many applications will use the Refresh/Repaint request command to update the information in the window also so much of what you experience will be dependent on the application. I'm sure I've messed up some of the details but that is the idea behind it.

Every display has refresh rate. Its how fast a frame is displaied on the screen. Refresh is just erase the old frame and display the next.

As one poster pointed out, "refresh" means different things to different people. But as you pointed out that you're an electrical engineer, I'll assume you're asking from an electronics perspective.

When you refresh a screen (in the CRT sense, not the LCD sense) you are re-painting the raster. Starting at the top-left corner, the electron beam repeatedly sweeps across the screen from left-to-right, exciting the phosphors on the interior face of the screen. In a color display, three electron beams are swept as a unit, one beam for each of the red, green, and blue phosphors. After the beam has reached the right edge of the screen, it begins at the left edge and sweeps across again, but this time slightly below the first "line."

As the beam is scanned in this way, the video memory is read out synchronously with the beam's position so that every pixel location in video RAM corresponds to a precise physical location on the screen. The currents from the three electron guns at the back of the CRT are modulated by the color values stored at each pixel address in video RAM. The digital values are converted to analog voltages (or currents, depending on the specific implementation) that determine the three electron-gun currents. The currents, in turn, determine the intensity of each of the R,G,B colors at that location on the screen. The combination of the R,G,B intensities determine the overall color of the "pixel" (pixel = PixEl = Picture Element). This is all highly simplified, of course, as a great deal of other electronics are involved.

If the screen is repainted fast enough, it appears to us as a solid image. In reality it is only an intense dot of light which changes color as it is rapidly swept across the screen. Phosphors have varying amounts of "persistence," or afterglow, but the duration of the afterglow is pretty short for most CRTs (in some specialized CRTs a long-persistance phosphor is used, but these are seldom color CRTs). If you slowed down the scan rate enough, you'd see this moving dot followed by a short trail of light, making it look like a comet. For refresh rates below a certain value called the "fusion frequency," below which the eye no longer integrates the scan into an image, the image begins to noticeably flicker. Older monitors had this problem because video RAM and especially, the video Digital-to-Analog converters (or Video DACs), available at the time simply weren't fast enough to handle the data rates needed for high resolution, high refresh-rate images.

Hopefully this answers the right question to a small degree.

-e

thank you for help

but when we referesh our screen it looks that information is updated for example if we made document file and save it but it will not appear in that folder unless we referesh the screen.

but your answer is very satisfactory thank you again

well not in to tooo much but it refresh the ram conatins

hi im habib i would also like 2 know what refreshing diuse 2 mi full siik comp

to update the memory cache to get latest value.but it x not used in linux.
The dynamic RAM needs to be refreshed so that it retains the data for a longer time. As for web pages the data is stored in the cache, and refreshing the webpage updates the cache with new set of information or values and the latest information is viewed.

I think now you got the answer..